The present invention relates to a device for locking and unlocking two mechanical members coupled for rotation as a unit, the device making use of a bistable elastic element. More particularly, the invention refers to a device for locking and unlocking a constant-velocity joint to and from the hub of a driving wheel of a vehicle, in particular an automobile. The bistable elastic element can deform elastically to shift alternately, under the action of a predetermined load, from and to first and second positions in which it takes different spatial arrangements.
In a previous pending patent application, to the same Applicant, there is disclosed a hub joint unit for a motor vehicle driving wheel, wherein the joint is coupled to the hub by means of a splined coupling with axially oriented toothing. The joint is axially locked to the hub by means of an expansion ring fitted in a circular seat formed in part on the joint and in part on the hub.
In such a unit, in order to mount and dismount the joint to and from the hub, particularly when servicing the vehicle, provided near the seat for the elastic ring are radial through apertures for inserting a tool to compress the locking ring radially and disengage it from the joint. However, this solution has the disadvantage of requiring the use of bulky tools that have to act on diametrically opposite positions of the elastic ring. Furthermore, the radial apertures put the inner parts of the joint in communication with the outside through the clearances of the splined coupling. As a result, dirt and moisture can penetrate in the joint.
Accordingly, an object of the present invention is to provide an improved locking/unlocking device capable of overcoming the disadvantages and limitations of the prior art. More particularly, it is a significant object of the present invention to provide a compact locking and unlocking device adapted to fit within the coupled members and operable from the outside, without jeopardising the sealing of the coupling.